The present embodiments relate to an apparatus for providing signal links between a first set of M signal connections and a second set of N signal connections. A first stage has first switching matrices with a total of N signal connections, and a second stage has a second switching matrix with a size of N×M with M signal connections.
An apparatus of this kind may, for example, be used in a magnetic resonance apparatus.
In magnetic resonance measurements, the interaction of magnetic moments of atomic nuclei, the nuclear spins, is investigated with an external magnetic field. The nuclear spins are aligned in the external magnetic field and precess with a Larmor frequency, which depends on the value of the magnetic moment of the atomic nucleus and the external magnetic field, around the axis of alignment in the magnetic field after excitation by an alternating external electromagnetic field. The atomic nuclei thereby generate an alternating electromagnetic field at the Larmor frequency.
With increasing magnetic field strengths, such as those used in present day magnetic resonance tomography systems, the Larmor frequency also increases so that, with the increasingly shorter wavelengths, reflections and interferences of the alternating electromagnetic fields occur. Arrangements at the transmitting end with a plurality of antenna coils and transmitting devices are used to compensate for the reflections and interference. At the same time, spatially localized reception via a plurality of antenna coils supplying signals that are orthogonal to one another, with the simultaneous evaluation of the signals via a plurality of independent receiving devices, enables quicker acquisition of a visual reproduction of the object under investigation.
In order to enable an optimal operating procedure when examining a patient, a significantly higher number of antenna coils are positioned on the patient and connected electrically to the magnetic resonance tomography system. The number is higher than are specifically evaluated during a specific measurement. Therefore, the number of possible connection points are substantially determined by the course of the operating procedure, while, for economic reasons, the number of receiving devices are restricted by the highest number of channels to be evaluated simultaneously. In this case, the assignment of antenna coils to transmitting and/or receiving devices is insofar flexible in that it is not necessary to connect a certain device to a certain antenna coil. The assignment may be taken into account later during the evaluation of the signals; it only has to be known.
However, a comparable apparatus may be used in other fields when necessary to establish a signal link between two sets of objects, wherein the elements in the second set are interchangeable. Here, ‘interchangeable’ means the fact that no specific assignment of an element in the first set to a specific element in the second set is necessary, instead the element in the first set may be connected to any element in the second set.
Possible fields of application may, for example, be circuits in the mobile radio service when one or more spare transmitters are available and are to be connected to an antenna if one transmitter fails. Also conceivable is usage in computer networks, for example when computer nodes are to be used as efficiently as possible in a parallel computer in that each free computer node is connected to an input/output processor. It is also possible for comparable apparatuses to be used within a computer, for example in a graphics controller with only a limited number of computing units that are to be utilized as efficiently as possible.
Different types of switching technology for connection problems of this type are known from the prior art.
Logically, the simplest are single-stage matrices with N inputs and M outputs clamping a matrix with N*M intersection points. Provided at each intersection point is a switching element, which may provide a signal link between input and output. In this case, it is possible to connect any input with any output. It is also known which switching element is to be switched to establish this link, namely the element at the respective intersection point of the signal input with the signal output.
However, the number of the switching elements is high and increases quadratically with the number of connections.
Known from switching technology for telephony are other two-stage or multi-stage switching networks, for example the so-called Clos network. These networks are designed to establish a signal link between predetermined connections at both ends with the greatest possible probability of the provision of a free signal link.